"High detailed mods without optimization" how can we know that,exactly?Hacker'z

Simple :- Using lower texture size does help. Even more if you use LOD0 elements which tend to have a high polycount- You can use a single texture for multiple parts , by assing the correct shaders , for example if you have a buper which contains plastic , shiny parts and paint , instead of using different textures for each , you can assign them to the same texture but with a different shader- The management of the parts , each part known can be used. Even if it's not in the way that everyone expects. xD- Avoid merging too much parts into once. If you want to add details , you can do it on parts which has less polygons.- The polycount limit is about 25000 triangles for each part , because of EAGL.

I'm not a master but these are the most common things that I do. And also testing , testing everytime to be accurate. If you saw a bug appearing suddenly, you'll be able to figure out the culprit and fix it asap. :)